Fuel burner



Nov. 28, 1944. Q F, CAMPBELL- 2,363,942

` FUEL BURNER Filed Feb. 17, 1942 2 sheets-sheet 1 INVENTOR 0in/erfampdl Nov.- 28,1944. o. F. CAMPBELL 'I v 2,363,942

FUEL BURNER .Filed Feb. 17, 1942 2 sheets-sheet 2 4INVEN'roR O Zz'ver556203055X/ BY 1 fmmwms Patented Nov. 28,1944

UNITED STATES PATENT OFFICE FUEL BURNER oiiverr. campbell, Whiting.Ind., miglior-tn Sinclair Refining Company, New York, N. Y., acorporation of Maine Application February 17, 1942, Serial No. 431,233 A(ci. 11o- 104) Claims.

This invention relates to fuel burners and more particularly relates toan improved burner especially adapted to the burning of finely dividedsolid fuels, such as powdered coal, and capable of operating efficientlyover a broad range of capacities.

The improved burner of my present invention is especially designed toinject into the com bustion zone of the furnace with which it is used a,relatively broad,- thin stream o f a suspension of solid fuel in agaseous medium, for example powdered coal suspended in air. This fuelstream may be directed along a generally horil zontal or verticalplaneor Vat an angle there-- with and a particular advantage of my improvedburner is its .ability to direct and to shape the resultant flame in amanner best suited to the design of thefparticular furnace with which itis used.

In the burning of nely divided solid fuels, the fuel is usually suppliedto the burner suspended in air. The stream'of air in which the fuel issuspended-constitutes 'a portion of the air required for combustion ofthe fuel. However, ad-

ditional air is required for combustion and this additionalair is'herein designated secondary air Y l A serious disadvantage ofconventional burners for burning a powdered solid fuel has -been thenarrow range 'of capacities at which the burner could be operated atmaximum eiliciency. For efficient operation, it is essential that therelative proportions of fuel and air be maintained at an optimum valueand that the fuel and air be intimately admixed upon entering thecombustion zone.

Some fuel burners are adapted to' operate sufficient that the optimumproportions of fuel and air be maintained.v It is also essential toefficient combustion that the fuel and air be properly mixed, that thefuel be highly dispersed in the combustion air.

One of the major defects of conventional `burners has been their failureto accomplish too 'low to accomplish adequate mixing, and

poor' combustion results.v If an attempt is made still further todecrease the capacity of such burners, a lower limit is soon reached.beyond which ignition cannot be maintained.

Burners vhaving air ducts of xed cross-sectional area may, of course, bedesigned for low capacity operation. However, if one attempts to operatesuch low capacity burners at considerably higher capacities eithersuillcient air cannot be supplied for efficient combustion or thevelocity of the air stream is apt to be so great as to extinguish theflame.

Numerous attempts have been made to overcome the capacity rangedeficiency ofconventional fuel burners'. Fortinstance, it has beenproposedto increase the flexibility of the burners with respect tocapacity range by providing mechanical means for varying thecross-sectional efficiently only at a given capacity or at a. capacitywhich cannot be changed while the burner is in operation. The capacityof other conventional burners may be changed vat will over a limitedrange by varying the amount of fuel and combustion air injected therebyinto the combustion zone. In the latter type of burner, when it `becomesdesirable to increase themate of heating cfa boiler, for instance, therate at' by the burner, is increased and, when al lower rate of heatingis desired, the rate at which the fuel is supplied is decreased.

If ecient operation is to be maintained over a range of heating rates,these variations in. the rate of fuel upply must be accompanied by theappropriate change in the amount of air supplied by the burner. However,it isvnot alone .which fuel is'supplied to the combustion zone area o fthe air duct at the point where it enters the mixing zone. Thus, whendecreased volumes ofv air are required, the cross-sectional area of theair duct exit would be decreased so as to maintain velocity and`turbulence of the air stream at the point where it meets with the fuelstream. One of the primary difficulties with such previously proposedarrangements has been the necessity of having moving parts locatedwithinthe zone of high temperature where vthey soon cease to :functionand another has been .their inability adequately to extendthe range ofemcient operating capacities.

Further attempts to extend the capacity 'range of conventional burnershave led to the suggestion that a plurality of air ducts be proiddedwith means removed from the heating zone for ccntrolling the passage ofair through the respec-f tive ducts. However, such suggestions, so `faras I am aware, have not heretofore resulted in a burner having theexibility and other advantageous characteristics combined in the burnerof my present invention.

In my co-pending application Serial No.

'389,518, med April 21, 1941, (now Patent No.

2,334,314 issued November 16, 1943) I have described and claimed animproved burner provided with a, plurality-of co-axially arranged ductsof annular cross-section and co-ai'dally positioned with respect to thefuel injection means. The passage of air through the respec t-ive ductsof the burner there described is conltrolled by a damper adapted topermit the passage of air first through the innermost duct only andprogressively through additional adjacent outer ducts as the damper ismoved from the closed to the open position. The burner of the presentinvention in some respects resembles that of my said co-pendingapplication but it Apossesses certain additional advantages as willhereinafter appear.

generally rectangular shape, as shown in Fig. 2

of the drawings. A

Above and below the nozzle 5 are laminated banks of air ducts 9 eachconsisting of a plurality of parallel airv ducts formed by a plfuralityof parallel plates I9 and side plates II. These banks of dructs are sopositioned that the parallel planes of the respective ducts form acuteIn the operation of the burner of my present invention a stream offinely divided solid fuel suspended in a gaseous medium is injected intothe combustion zone of the furnace through a nozzle having an exit portof considerably greater dimension along one plane than along the planeperpendicular thereto, such, for example, as a iishtail or fan-shapednozzle, so that the fuel suspension enters the combustion zone in arelatively broad, thin stream. The secondary air is supplied through`laminated banks of air duets arranged on each of the broad sides of thefuel nozzle and so positioned with respect thereto as to direct thestreams of the secondary air issuing therefrom toward the fuel streamfrom above and below. The passage of air through the respective ducts isso controlled by dampers, without the high temperature zone, that, whenoperating at minimum capacity, the secondary air is admitted through theinnermost ducts only and, as the operating rate is increased, additionalfuel and secondary air being supplied, the secondary air is admitted,progressively through additional adjacent outer ducts. l

The invention will be further described with reference to theaccompanying drawings which represent a specic embodiment of myinvention. It will be understood, however, that my invention is notlimited to the specific arrangement shown.

Fig. 1 of the drawings isa vertical cross-sectional view of the burneralong the line I--I of Fig. 2 of the drawings which is a front elevationview thereof. the drawings. .like parts numerals.

In the drawings-the burner housing I is shown are indicated by likeangles with the plane of the nozzle and intersect that plane in linesperpendicular to the axis of the nozzle beyond the exit end of thenozzle.

These banks of air ducts 9 are sealed into the firing port 3 by means ofplates I2 and side-seal plates I8 so as to avoid the uncontrolled-entrance of air to the combustion chamber through openings in thefiring port. Extending through the side-seal plates I3 are the lighterports I4.

The outer ends of these ducts 9 terminate in a register or grating I5 towhich the parallel plates II) are fastened so that the respective ductsregister with the openings in the gratings. These registers are in turnsupported by the nozzle 5 and the supporting members I8.

The passage of air through the several ducts ls controlled by the damperplates Il adapted to be moved across the registers I5 in the'directionof the furnace by means of 'the rack and 40 pinions I8, shafts i9, bevelgears 20, shafts 2l and the handwheels 22. A r

In Fig. 1 of the drawings, the dampers I1 are show n in the extreme leftposition. .In this position the entrances to all of the secondary airducts are closed. As the dampers are moved froml this position towardthe furnace, the entrancesto the innermost ducts only are first openedand, as the damper is moved still further toward theright entrances tokvsuccessive additional outer ducts, are progressively opened.

It is sometimes desirable, in order better to forming the duct. Thesedivision members may In the respective figures of attached to the wall 2ofV a furnace at the firing port 3 by means of-brackets 4. Within theburner housing and supported thereby is the burner nozzle 5 throughwhich the fuel suspension is injected into the combustion chamber 6. Thefuel suspension is supplied to the burner nozzle 5 in variablequantities, depending upon the operating. capacityldesired, from anyconvenient source, not shown, through the conduit 1. .v

The usual practice in the operation of burners of this type is to`reduce the solid fuel to the `desired fineness by conventional grindersAor the like and to suspend the 'finely ydivided fuel in ail begenerally parallel to the vertical plane through the axis of the burnerand may be staggered as shown. I f desired, these division members maybe placed at an angle with said vertical plane so as to concentrate thesecondary air at theA inner portion or at the outer edges of the flame.

ducts may be supported by gratings or registers,`

as indicated in the drawings at 28,-'fer the innercrease the velocity-of the air stream passing therefrom. This increased velocity issometimes If desired, the parallel plates-forming n housing I.

aaeaua The outer ends of the ducts 9 terminate in the v air chamber orwindbox 23 formed by the burning Air may be supplied to the windboxthrough a suitable opening such as the conduit 24. Where the furnace isto be operated under forced draft conditions, the conduit 24 may beconnected with a conventional air propulsion means.v not shown, andwhere natural draft conditions are to be used, the windbox 23 or theconduit 24 may be open to the atmosphere.

In the operation of the burner shown, the fuel suspension supplied tothe burner through the conduit 1 under pressure passes through thenozzle 5 and is injected into the'combustion zone 6 in a relatively-thin fan-shaped stream. This fuel suspension includes a portion of theair required for combustionof the suspended fuel but not the entirerequirement. Secondary air is' supplied through the laminated duct banks9 and for maximum combustion eiliciency this secondary air must becomeintimately admixed with the suspended fuel in the combustion zone.

The thoroughness of this mixing is dependent lupon the volume ofsecondary air required,

velocities inadequate for proper mixing would result when the volume ofsecondary airis reduced to meet reduced fuel injection. In the operationof my improved burner, .optimum velocities of the secondary vair forproper mixing i.

are obtained over a wide range of operating capacities by increasing ordecreasing the number of ducts through which the secondary air issupplied in accordancewith the amount of fuel being burned andconsequently the amount of secondary air required. V

However, vcontrol of velocity alone o f the entering secondary airstream or streams is not sumcient to effect optimum mixing. Thel pointof 4introduction of the secondary air stream or streams and the shape ofthe injected fuel stream are also of major importance. iIn my improvedburner, the secondary air ducts are so positioned with respect to thefuel nozzle `as to direct the air streams therefrom into the thin,laterally extended fuel stream from above and below at points near ,itsexit from. the fuel nozzle. The amounts of secondary air so directedagainst the upper and lower sides of the fuel stream vmay be equal ormay be so proportioned as to direct or shape the flame to meetspecial.furnace conditions. i I

When operating at minimum capacity, the velocity of the incoming fuelstream is naturally reduced. Under such conditions, better mixing isobtained by directing the reduced amount -of stream having a largesurface area per unit of volume and the introduction of the secondaryairat the optimum velocity and at the optimum point with respect to`thefuel stream.

These dampers as shown in the drawings, are adapted to be individuallycontrolled manually. If desired, the movement o'f .the upper and lowerdampers may be correlated by suitable linkages not shown' or theirmovement may be automatically controlled by conventional meansresponsiveto the amount of fuel supply, or the like.

' In the drawings, I have shown my improved burner so positioned thatthe fan-shaped-fuel stream therefrom is injected into the combustionchamber in a generally horizontal plane. It will be understood, however,that the position of the burner may be varied to meet the firing orflameshaping requirements of particular furnaces with which it is to beused.

I claim:

1. In a fuel burner for burning finely-divided vsolid fuel suspended ina gaseous medium the improvement which comprises a fuel injection nozzlehaving a relatively broad, thin exit port, two banksof air ducts eachbankcomprising a plurality of substantially parallel air ductssubstantially co-extensive in breadth with the breadth of the nozzleexit port, one bank being positioned on each of the opposite broad sidessolid fuel suspended in a gaseous medium theimprovement which comprisesa fuel injection nozzle having a relatively broad, thin exit port.

two banks of air ducts each bank comprising a plurality of substantiallyparallel air ducts sub.v stantiallyco-extensive in breadth with thevbreadth of the nozzle exit port, one bank being positioned on each ofthe opposite broad sides of 65 the nozzle exit port so that the parallelplanes of secondary air into the fuel stream at a lpoint v:lust beyondthe exitof the latter from the fuel nozzle. Even when operating athigher capacities, it is desirable to introduce a portion of the jbination of `advantages derived from the injection of the fuel into thecombustion chamber` in a the respective ducts form acute angles with thelongitudinal plane of the nozzle exit port and intersect saidlongitudinal plane extended inwardly from said port, a damper for each-bank of air Vprising a sliding plate member adapted to close each ofthe ducts of the bank when in the` extreme closed position, to admit airthrough each of the ductsy of the' bank when in the extreme openposition and to open first the innermost duct only of the respectivebanks and progressively to open additional successively outer ductsthereof as the sliding plate member is moved from the closed tothe openposition.

3. In a fuel burner for burning finely-divided solid fuel suspended in agaseous medium the improvement which comprises a fuel injection nozzlehaving a relatively broad, thin exit port, two banks of air ducts eachbank comprising a ofl air ducts for controlling the passage of air ductsfor controlling the passage of air lthrough the respective ductsthereof, said damper complurality of substantially parallel air ductssubstantially co-extensive in breadthwith the breadth oi! the nozzleexit port, one bank being positioned on each ofthe opposite broad sidesoi' the nozzle exit port so that the parallel planes oi the respectiveducts form acute angles with the longitudinal plane of the nozzle exitport and intersect said longitudinal plane extended inwardly from saidport beyond the exit port in. lines substantially parallel to theverticalplane of said port, a damper for each bank of air ducts forcontrolling the passage oi' air through the respective ducts thereof,'said damper comprising a member adapted'to close each of the ducts ofthe bank whenin the extreme closed position, to

admit air through each of the ducts of the bank when in thel extremeopen position and to open ilrst the innermost duct only of therespective banks and 'progressively to open additional successivelyouter ducts thereof as' the damper member is moved from the closedposition to the open position.

4. Ina fuelburner for burning tlne1ydlvided solid fuel suspended in agaseous medium the improvenient which vcomprises a fuel ,injectionnozzle having a relatively broad, thin exit port, two banks of air ductseach bank comprising a plurality of substantially parallel air ductssub.- stantially co-extensive in breadth with the breadth of the nozzleexit port, one'bank. being positioned on each ofthe opposite broad sidesof the nozzleexit port so that the parallel planes oi' the respectiveducts form acute angles with the longitudinal plane oi.' the nozzle exitport and intersect said l ngitudinal plane extended inwardly from saiport, division members extending through the respective ducts so as todivide the ducts into a plurality oi passages running toward the exitends thereof, a damper for each bank of air ducts for controlling thepassage oi' air through the respective ducts thereof,

damper comprising a member adapted to close each oi' the ducts ofthe-bank when in the extreme dosed position, to admitan through each orthe ducts oi the bank when in the extreme open position and to openfirst the innermost duct only of the respective banks `and progressivelyto open additional successivelyouter ducts thereof as the damper memberis mved from the closed position to the open position.

5. In a fuel burner for burning iinely-divided solid fuel suspended in agaseous medium the improvement which comprises a fuel injection nozzlehaving a relatively broad, thin exit port, two banks of air ducts eachbankcomprising a plurality o! substantially parallel air ductssubstantially cao-extensive in breadth with the breadth of the nozzleexit port, one bank being positioned on each of the opposite broad sidesof the nozzle exit port so that the parallel planes of the respectiveducts form acute-angles with the longitudinal plane of the nozzle exitport and the bank when in the extreme closed position, to

admit air through each of the ducts of the bank when in the extreme openposition and to open first the innermost duct only oi.' thev respectivebanks and progressively to open additional successively outer ductsthereof'as the damper member is moved from the closed position to theopen position.

' OLIVER r'. CAMPBELL.

